Command is not executing when local player is not host

Question

I am getting very strange behavior, if my player instantiate as host (Server+Player) then my command function runs perfectly and certain object become instantiate but if I join the host then my Command doesn't execute on my local player but runs on all other clients.

void Start()
{
    if (isLocalPlayer)
    {
        Debug.Log("It is VR Player spawn-Start");
        SetVRLocalPlayerSetting();
        //InstantiateMimicVRHeadAndController();
        CmdInstantiateMimicVRHeadAndController();
    }
    else
    {
        Debug.Log("It is not vr Player its not isLocalPlayer");
        DisableSelectedMonobevaiourScripts();
    }
}
[Command]//This function have a problem
public void CmdInstantiateMimicVRHeadAndController() { 
    Debug.Log("instantiateing the controller and head object");
    vrHeadCopyObj = (GameObject) Instantiate(vrHeadObjPrefab);
    vrRightCtrlCopyObj = (GameObject) Instantiate(vrRightCtrlPrefab);
    vrLeftCtrlCopyObj = (GameObject) Instantiate(vrLeftCtrlPrefab);

    // spawn the bullet on the clients
    NetworkServer.Spawn(vrHeadCopyObj);
    NetworkServer.Spawn(vrRightCtrlCopyObj);
    NetworkServer.Spawn(vrLeftCtrlCopyObj);     
}